This invention relates to a method for stabilizing pellets of a hydrogenation catalyst from deterioration during a hydrogenation process and more particularly, the use of a metal melting below about 400.degree. C. for such stabilization.
Pelletized catalysts, especially those used in fixed bed type reactors, are subject to physical degradation during use. Such degradation produces fine particles which can result in the plugging of the bed and in the need for replacing the catalyst pellets even though the catalyst material is otherwise still effective.
U.S. Pat. No. 2,116,552 issued to H. Arnold sets forth a method for the preparation and use of a catalyst for the hydrogenation of carboxylic acids. The catalyst comprises a ferrous metal or their compounds wherein the ferrous metal is iron, cobalt and nickel combined with a large quantity, about 10% by weight of a low melting point metal such as cadmium which mixture has been heated at a temperature between about 300.degree. and 400.degree. C. and then broken up into a powder which can go through an 8 to 14 mesh or a 60 mesh. The patent sets forth the fact that such a powdered catalyst, when used for the hydrogenation of carboxylic acid, yields less by-products than a similar catalyst without the use of the low melting point metal.
A method for stabilizing pellets or tablets of a hydrogenation catalyst during use is set forth in coassigned U.S. Pat. No. 3,384,666, wherein from about 0.5 to about 1 percent of a base selected from the class consisting of the hydroxides and alkoxides of sodium, lithium and potassium are added to the hydrogenation catalyst. The hydrogenation catalyst consists primarily of a first component selected from the class consisting of nickel and cobalt, and also copper and a small amount of a nonreducible metal oxide.
U.S. Pat. No. 2,229,199 sets forth a method for preparing strong catalysts which are stable at high temperatures of the order of 900.degree. F. and upwards by combining the catalyst, here preferably nickel, with a substantial amount of a metal oxide not reducible with hydrogen under the conditions of the reaction that the catalyst is to be used for, and a lubricant comprising graphite. The mixture is then compressed into dense lumps of a predetermined configuration, and the lumps are heated in an oxidizing atmosphere until the graphite is removed. The resulting lumps are then heated in a reducing atmosphere at a sufficiently high temperature to effect the conversion of nickel oxide to nickel. This nickel catalyst is preferably used for producing hydrogen gas by passing a hydrocarbon vapor and steam or carbon monoxide over the catalyst.